1. Field of the Invention
This invention relates to an improved method and apparatus for fluidized texturizing yarn. In a further aspect, the invention relates to a fluidized bounce crimp texturizing method, and apparatus therefor, wherein the thickness or a minute accumulation of the yarn issuing from the fluidized bounce crimp texturizer (bounce crimper) is sensed and the rate at which the texturized yarn collected regulated to maintain the thickness or limit the accumulation of the texturized yarn within certain predetermined limits.
2. The Prior Art
Synthetic thermoplastic yarn materials are produced as a number of continuous, straight, smooth filaments. Such yarns have little bulk, and their utility in textile applications is thus rather limited.
In order to enhance the bulk and texture of synthetic yarns, a variety of crimping processes have been used in the past. One common technique which has been used for thermoplastic yarns is to bend the yarn filaments and heat the yarn while the filaments are in bent or crimped configurations.
One especially good texturizing technique, in terms of yielding a high-bulked yarn, is known as "rebound" or "bounce crimping".
Bounce crimping entails hurling yarn, propelled by a heated fluid through a jet, in a continuous streamlike flow against a foraminous surface upon which the yarn impinges and from which the yarn instantaneously rebounds or bounces. The impact of the yarn upon the foraminous surface axially buckles and crimps individual filaments of the yarn while the heated fluid passes through the foraminous surface. The texturized yarn progresses without tension and substantially by rebound inertia away from the crimping zone and, in the prior art process, is guided to a collection station where the yarn is heated and then cooled to heat-set the crimp prior to winding upon a storage spool.
Thermoplastic yarn texturized by the foregoing bounce crimping process possesses, inter alia, exceptional covering capability and a high degree of resiliency; note U.S. Pat. No. 3,686,848.
The basic process and apparatus for practicing the bounce crimp texturizing process is described by Clarkson in U.S. Pat. No. 3,665,567. Briefly, the Clarkson process entails feeding a yarn through an elongate slender tube by a jet of steam and hurling the yarn longitudinally against a foraminous screen causing it to buckle in a random manner and bounce away in a random array. The yarn is thereby crimped or texturized and freely rebounds laterally through a passage from which it drops down to a receiver for heat-setting. The steam primarily passes through the foraminous screen and is collected.
In order to properly conduct bounce crimping, it is important that the yarn is rebounded from the screen and discharged from the bounce crimper under essentially no tension. The yarn cannot be pulled from the bounce crimper, since tension on the yarn at this point could pull the crimp from the yarn and could also cause the foraminous screen to be bypassed.
Various improvements in bounce crimp texturizing processes and apparatus are described in U.S. Pat. Nos. 3,859,696, 3,859,697, 3,879,819 and 3,887,971. All of the apparatus and processes described in these patents and in U.S. Pat. No. 3,665,567 are characterized by the use of a J-tube type yarn accumulator wherein the yarn is accumulated (piled) and heat-treated (heat-set and cooled). In U.S. Pat. No. 3,879,819, the J-tube is provided with a photocell light sensing means for maintaining a certain height (pile) of yarn in the J-tube by regulating the yarn windup speed in response to the sensing means.
The J-tube accumulator was used by the prior art to heat-set the crimp on the yarn and to ensure that the yarn rebounded from the bounce crimp screen in a tensionless state by permitting the yarn to free-fall into the accumulator from the bounce crimper. Subsequently, the J-tube was primarily used only for the second purpose.
In accumulating or piling the yarn, tangles were found to occur, resulting in localized pulling on the yarn as it was wound up, thus causing the crimp to be pulled out of random segments of the yarn and/or the yarn to break. The frequency of these breaks necessitated an increase in the number of operators required to operate or monitor a given number of texturizing machines and rethread the yarn when breaks occur.
Also, where low-denier yarns (e.g., about 500 denier or less) are used, the problem is magnified such that accumulator systems cannot be efficiently used. This magnification is believed caused by the fact that the lower the denier, the more loops or coils that are in contact with each other in the accumulator. Hence, the more contact, the more chance there is for filaments of the various loops to tangle with each other. This increased contact, coupled with the lower weight of the loops or coils, substantially increases the likelihood of the loops being pulled out of the accumulator, resulting in increased piling and tangles, etc.